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Physics · PYQ NEET UG 2018
हिन्दीTwo wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by \( \Delta l \) on applying a force F, how much force is needed to stretch the second wire by the same amount?
Correct answer · Option 1
9 F
Explanation
Volume \( V = Al = \text{constant} \). If area becomes \( 3A \), length becomes \( l/3 \). Force \( F = \frac{YA\Delta l}{l} \). For wire 2, \( F' = \frac{Y(3A)\Delta l}{(l/3)} = 9\frac{YA\Delta l}{l} = 9F \).
